<template>
  <div class="slider" ref="slider">
    <div class="slider-group" ref="sliderGroup">
      <slot>
      </slot>
    </div>
    <div class="dots">
      <span class="dot" v-for="(item,index) in dots" :key="index" :class="{active: currentPageIndex===index}"></span>
    </div>
  </div>
</template>

<script>
import BScroll from 'better-scroll'
import {addClass} from 'common/js/dom'
export default {
  props:{
    loop:{
      type:Boolean,
      default:true
    },
    autoPlay:{
      type:Boolean,
      default:true
    },
    interval:{
      type: Number,
      default:4000
    }
  },data(){
    return{
      dots: [],
      currentPageIndex: 0,
    }
    },
  mounted(){
    setTimeout(()=>{
      this._setSliderwidth()
      this._initDots()
      this._initSlider()
      if(this.loop){
        this._play()
      }
    },20)

    window.addEventListener('resize',()=>{
      if(!this.slider){
        return
      }
      this._setSliderwidth(true)
      this.slider.refresh()
    })
  },
  methods:{
    _setSliderwidth(isResize){
      this.children = this.$refs.sliderGroup.children


      let width = 0
      let sliderWidth = this.$refs.slider.clientWidth
      for(let i = 0;i < this.children.length;i++){
        let child = this.children[i]
        addClass(child,'slider-item')
        child.style.width = sliderWidth + 'px'
        width += sliderWidth
      }
      if(this.loop&&!isResize){
        width += 2*sliderWidth //左右各有一个dom，要加二
      }
      
      this.$refs.sliderGroup.style.width=width + 'px'
    },
    _initDots(){
      this.dots=new Array(this.children.length)
    },
    _initSlider(){
      this.slider = new BScroll(this.$refs.slider,{
        scrollX: true,
        scrollY: false,
        momentum: false,
        snap: true,
        snapLoop: this.loop,
        snapThreshold: 0.3,
        snapSpeed: 400
      }),
      this.slider.on('scrollEnd',()=>{
        this.currentPageIndex=this.slider.getCurrentPage().pageX
        if(this.loop){
          this.currentPageIndex -= 1
        }
        if(this.autoPlay){
          clearTimeout()
          this._play()          
        }
      })
    },
    _play(){
      let pageIndex = this.currentPageIndex + 1
      if(this.loop){
        pageIndex += 1
      }
      let timer = setTimeout((()=>{
        this.slider.goToPage(pageIndex,0,400)
      }),this.interval)
    }
  },destroyed(){
    clearTimeout(this.timer)
  }
}
</script>

<style lang="stylus" scoped>
  @import "~common/stylus/variable"

  .slider
    min-height 1px
    .slider-group
      position relative
      overflow hidden
      white-space nowrap
      .slider-item
        float left
        box-sizing border-box
        overflow hidden
        text-align center
        a
          display block
          width 100%
          overflow hidden
          text-decoration none
        img
          display: block
          width: 100%
    .dots
      position: absolute
      right: 0
      left: 0
      bottom: 12px
      text-align: center
      font-size: 0
      .dot
        display: inline-block
        margin: 0 4px
        width: 8px
        height: 8px
        border-radius: 50%
        background: $color-text-l
        &.active
          width: 20px
          border-radius: 5px
          background: $color-text-ll

</style>

